Note: Descriptions are shown in the official language in which they were submitted.
3'P.~i'91~i
The field of -the invention i,s input/output
interface racks for control systems such as proyram-
mable controllers, process controls and numerical
controls, and particularly, means ~or mounting a
number of input and output interface circuits for
such a control system and connecting them to the
machine being controlled.
In electrical control systems such as solid
state controllers, numerical controls, programmable
controllers and process controls, the circuits
whieh interfaee the system to the machine being
controlled are typically mounted on printed circuit
boards which are arranged alongside one another and
are interconnected by a wiring harness or a "mother ~-~
board." The electrical connection of such interface
circuits to the machine being controlled is made
by the user and it may involve the connection of
hundreds or even thousands of wires to terminals on
the inter~ace circuit boards.
In I/0 interface racks such as those disclosed
in U.S. Patent Nos. 3,992,654 and 3,942,077, the
wire terminals on eaeh interfaee circuit board are
disposed along its front edge where they are readily
accessible to maintenanee personnel. In most applica-
tions these wire terminals are not connected directly
to the controlled machine, but instead, are conneeted
thereto through a terminal block which is mounted
within the same enclosure as the I/O interface rack.
Terminal blocks such as that disclosed in U.S. Patent
No. 3,236,975 are often employed for this purpose because
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they are suitable for use in industrial environments.
Such terminal blocks are rugged and have been employed
for years in industry when "field wiring" is necessary.
In prior I/O interface racks it becomes necessary to
hand wire the terminals on the interface circuit
boards to the heavy duty wire terminals in addition to
hand wiring those terminals to the devices on the
controlled machine. This additional hand wiring adds
considerably to the overall cost of the control system.
The present invention relates to an I/O interface
rack for a control system, and particularly, to one
which supports a mother board between a pair of spaced
side plates and which mounts a terminal block along
i one edge of the mother board which is electrically
connected to the conductive path network on the mother
board. A plurality of I/O interface circuits disposed
on printed circuit boards plug into connectors on the - ~ -
mother board and are firmly mounted thereto between
the side plates. All field wiring is done directly on
the terminal block which electrically connects to the -
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I/O interface circuits through the mother board and
- associated connectors.
The invention will enable one to provide a compact -
and rugged I/O interface rack which allows field
wiring directly to the interface circuit terminals.
Rather than providing wire terminals along the front
edge of each interface circuit printed circuit board,
electrical connections are made through the connector to
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the mother board and directly to the terminal block.
These connections are provided in the printed circuitry
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and no hand wiring is required.
The invention will also enable one to provide
an interface rack in which I/O modules may be removed
or replaced without disconnecting or reconnecting
wires. All wiring is connected to the terminal blocks
and coupled through the mother board and connectors to
the appropriate I/O module. These conneckions are
broken merely by pulling the module free of its connector~
" The invention will further enable one to facilitate
the removal and replacement of I/O modules. Only two
mounting screws need be loosened to unfasten each
moduleO These mounting screws are retained to the
module case and, therefore, when the module is pulled ~
free, there are no parts which can fall and become lost. ~-
In drawings which illustrate the embodiment of
the invention,
I Fig. 1 is a perspective view of the invention with
; two modules removed,
Fig. 2 is a front elevation view of the invention
wi~h one module removed,
Fig. 3 is a side elevation view of the invention
with parts cut away and selected modules partially
removed,
Fig. 4 is a partial perspective view of the terminal
block which forms part of the invention of Figs. 1-3,
Figs. 5a-c are left side, right side and top
elevation views of a module which forms part of the
invention of Figs. 1-3~ and
Fig. 6 is a partial top view of the invented
interface rack.
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~ eferring particularly to Figs. 1-3, the I/O
interface rack includes a pair of spaced metal side
plates 1 and 2 which have integral mounting ears 3
., .
and 4 that extend outward along their entire back
edge. The ears 3 and 4 each include a pair of slots
- 5 and 6 which face outward and are suitable for ,,
receiving mounting bolts (not shown in the drawings).
Typically, the I/O interface rack is mounted to the
back wall of an enclosed cabinet (not shown in the
' 10 drawings) which also houses other I/O interface racks
and a programmable controller processor such as that
disclosed in U.S. ~atent No. 4,165,53~ which issued :
August 21, 197g and is entitled "Digital Control System , ,
With Boolean Processor."
~ 15 As shown best in Figs. 2 and 3, three circuit ~,
'~ board mounting bars 7-9 extend between the side plates ''~' '
1 and 2 and are fastened thereto by screws 10. The
mounting bars 7-9 are equally spacecl and are disposed '~'
, in a common back plane. A rectangular shaped mother
board, or circuit board 11 is ~astened to the mounting
bars 7-9 and is disposed in the back plane defined
by them. The circuit board 11 includes a network of
conductive paths on both its surfaces which are formed
from etched metal foil. The circuit board 11 extends
', 25 between the upright side plates 1 and 2, and together
they define a shallow cavity indicated generally at 12.
As shown best in Figs. 2 and 3, three module,
mounting b~rs 13-15 also extend between the side plates
, 1 and 2 and are fastened thereto by screws 16. These
30 mounting bars 13-15 are attached along the forward edge -~
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of the side plates 1 and 2 and they are, therefore,
in a common plane which is sub.stantlally forward of
the circuit board 11. The mounting bars 13-15 serve
not only to strengthen the framework which supports
the circuit board 11 and to thus minimize the twisting
forces thereon, but also, to guide and secure the
individual I/O modules as will be d~scribed hereinafter.
Mounted along opposing edges of the circuit board
11 and disposed on its front surface are terminal
blocks 17 and 18. As shown best in Fig. 4, the
terminal blocks 17 and 18 are similar to those dis-
closed in U.S. Patent No. 3,236,975 in which each is
releasably retained to metal mounting channels 19
and 20. The terminal blocks 17 and 18 are commercially
available in segments of various sizes and these
segments can be selectively position~d on the mounting -~
;~ channel 19 or 20 and snapped into place. The mounting
channels 19 and 20 are securely fastened by bolts
(not shown) which extend through the circuit board 11
~; 20 and into threaded engagement with the board mounting
bars 7 and 9 which lie directly therebeneath. They
extend the entire length of the circuit board 11 from ~ ;
one side plate to the other. - -
Referring particularly to Fig. 4, the terminal
blocks 17 and 18 include a molded plastic frame 21
which includes a plurality of spaced upright barrier
walls 22 that define terminal compartments therebetween.
Each compar~ment includes a wire terminal comprised
of a metallic cage 23 lnto which a wire 45 may be ~-
0 inserted and fastened by means of a screw 24. A tongue
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portion ~3 is formed on a metallic connector ~ and
it extends into the cage 23 and makes electrical
connection with the wire 45. The connector 44 also
has an integrally formed arm 46 which extends outward
to the opposite side of the frame 21. The arm 46
is bent downward at a right angle and its end extends
through an opening in the mother board 11 and is
soldered in place to the conductive network thereon.
All positions on the mounting channels 19 and 20
are occupied in the illustrated preferred embodiment,
however, it can be appreciated that some of the terminal
block segments may not be needed in certain installations ~
which do not require as many wire termination points. ~-
In addition to the flexibility in the number and -
position of the terminal block segments afforded by
this arrangement, the terminal blocks 17 and 18 provide
wire terminals of sufficient size and structure to
allow direct "field wiring" to the interface rack by
electxicians on the job site.
Referring particularly to Figs. 1-3, the I/O
interface rack mounts up to sixteen separate I/O
modules 25 and one adapter module 26~ The adapter
! module 26 is disposed along the right hand side plate
2, and although it is rather slender when viewed from
the front, it extends over the entire vertical extent
of the Gavity 12. The adapt~r module 26 fastens to
the upper and lower module mounting bars 13 and lS by
means of screws 27 and it electrically connects to
the circuit board 11 by means of an edge connector (not
shown in the drawings). As described in the above
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cited U.S. Patent No. ~,165,534 entitled "Diyital Control
System With soolean Processor", the adapter module 26
provides decoding and fault monitoring functions for
the entire I/O interface rack. It couples to the con-
troller processor and an adjacent I/O interface rackthrough cables which connect to respective connectors
; 28 and 29. Data flows through one of the connectors
28 and 29, through the adapter module circuitry and
into the conductive paths on the circuit board ll. The
adapter module circuitry also enables I/O modules to
respond to data or transmit data by signals conveyed ~ -~
thereto through conductive paths on the circuit board
; 11. In other words, all data conveyed between the
I/O modules 25 and the controller processor (not
shown in the drawings) ~lows through the circuit
board ll.
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Each I/O module 25 is electrically connected to `~
the circuit board 11 by an edge connector 30 which is
disposed on the ~ront surface of the circuit board ll
and within the cavity 12. The edge connectors 30 are
commercially available connectors such as the twin
leaf solder type mother board printcd circuit connector,
manufactured by AMP, Inc. which includes terminal pins
(not shown) that extend through openings in the
circuit board ll and solder to respective conductive
paths on its back sur~ace. Eight of the connectors 30
are spaced apart equally across the width of the I/O -~
interface rack above the module mounting bar 14 and
`~ ~ the remaining eight connectors 30 are similarly spa¢ed
beneath the module mounting har 14.
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As shown best in Fig. 3, each I/O module 25
includes a circuit board 31 which presents, or
; directs, an edge 32 toward its rear. The module
25 is mounted by inserting this edge 32 in the
appropriate edge connector 30 and by securely fasten-
ing the module 25 to the adjacent module mounting
bars 13 and 14 or 1~ and 15. Referring parricularly
to Figs. 2 and 5a-5c, the circuit board 31 in each
module 25 is substantially enclosed by a molded plastic
; 10 case 33. The case is generally rectangular in shape
and includes a relatively flat, rectangular front
surface 34. The case 33 also includes a pair of
oppositely directed support walls 35 and 36 and a pair
of feet 43 and 44 which extend from its back to engage
the mother board 11 when the module 25 is installed.
The feet 43 and 44 engage the ends of the connector
30 and serve to guide the module 24 into an accurate
;~ connection therewith. The support wall 35 is directed
upward when the I/O module 25 is mounted in place and
~ 20 a pair of spaced mounting tabs 37a and 37b extend
- upward therefrom. The mounting tabs 37a and 37b are ~ -
integrally molded with the upper wall 35 and they;~
rotatably retain and align a mounting screw 38. ~- ~
similar set of mounting tabs 39a and 39b extend from ~ -
the lower mounting wall 36 and they likewise support -
and retain a mounting screw 40. The mounting screws
33 and 40 are received in threaded openings 41 formed
in the module mounting bars 13, 14 and 15, and when
fastened thereto the tabs 37a and 39a are drawn tightly
against the front surfaces of the mounting bars. The
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modules 25 are thus tightly retained in place with
the conductive paths on their circuit bo~rds 31 in
electrical connection with the conductive paths on
the mother board 11.
Although spacing is provided between adjacent
I/O modules 25 to allow for their easy removal and
insertion, they are spaced closely enough to limit
the lateral extent to which each module can be moved.
As a result, adjacent modules 25 serve as a guideway
; 10 when inserting an I/O module 25 and the modules 25
provide support for one another against lateral forces. -
As shown best in Figs. 5b and 6, the middle portion of
- each module 25 is slightly narrower in width than its
rear and forward ends. When the modules 25 are
mounted adjacent to one another, therefore, substantial
passageways ~2 are formed therebetween which allow the
unobstructed flow of cooling air. The I/O modules
25 are aligned one above the other in the I/O inter-
face rack and these passageways 42 extend vertically
through the entire interface rack to cool the electrical
components therein. Also, many of the modules 25
include heat sinks 47 which communicate with the
passageways 42 and which help to establish an upward
flow of air therethrough.
An interface rack has been described which offers
` a number of advantages over prior structures. Individual -
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modules can be inserted or removed without disconnecting
any wires or disassembling any parts. The two mounting
screws 38 and 40 are retained to the case 33 and
although they must be rotated to remove or mount the :
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module, they will not fall free or into a live
electrical circuit. It is possihle, therefore, to
remove or replace I/O modules without powering down
the entire programmable controller system. Also, the
field wiring which is required to connect the I/O
interface rack with the machine to be controlled is
made directly to the terminal blocks 17 and 18. This
is in sharp contrast to prior systems in which separate
terminal hlocks are provided in the cabinet which
houses the interface rack and wires must be run between
these terminals and the individual I/O module terminals.
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